Impact polypropylene has seen wide use over the years with many applications. For example, JP 08027238 discloses a high transparency composition through viscosity matching of an impact copolymer rubber phase with the homopolymer phase wherein the ethylene content of the rubber phase is 25-65 w %. Additionally, JP 08165385 discloses impact copolymers containing 0.1-10% w ethylene and a rubber phase containing 30-90% w ethylene.
However, the dispersed copolymer phase particles are believed to scatter light by virtue of their size, and this results in an observed haze, and so impact copolymers have been thought not to be useful where applications require clarity. Rather, random copolymers, i.e., single phase polypropylene with a comonomer, have been used for such purposes. These random copolymers, though, do not have the necessary physical properties for applications where impact copolymers are used normally.
U.S. Pat. No. 4,634,740 to Fujita et al. discloses a relatively clear composition having 65 to 95% w of propylene homopolymer and 5 to 35% w of an ethylene-propylene rubber with 70 to 85% w ethylene; however, said compositions are not in situ blends, but are physical blends having poor physical properties. EP 0 373 660 confirms the physical property problems of such compositions. Fortunately, the impact copolymers of this invention solve these problems in that they have good clarity, as well as good physical properties.